This invention relates to methods of and apparatus for separating floating and suspended solids from a flowing liquid using continuous deflective separation, and particularly, but not solely to non-mechanical methods and apparatus.
More generally, the invention relates to apparatus and methods for separating solids or particulate matter from flowing liquids or gases. The invention has particular, although not exclusive, application to the filtration of floating and entrained solids from discharges of water. One particular application of the invention is in relation to storm water drain technology. There are many applications where it is desirable to separate solids from a flowing liquid including:
1. Separation of solids from stormwater.
In many areas of the world, stormwater is directed to waterways and seas. Stormwater is a major carrier of solid pollutants such as plastics, cans, tree branches and animal faeces, amongst other things to waterways and seas.
Endeavours have been made to limit the passage of at least some of these materials, one method used is by having grates across outlets from the drains but these have generally been unsatisfactory because the size of the grate must be such as to enable water to pass even if material is held against the grate by water pressure so it has been necessary that the grate be of substantial opening size. Also, even such grates can be blocked and it is essential to provide a flow path around or over the grate to prevent build up of water upstream in the drain system. A second alternative proposed has been the use of systems, such as cyclones and dynamic separators, to remove the waste. Whilst these can be efficient, they are too expensive to be used in the whole of a stormwater system.
2. Separation of liquid from sewage.
A major difficulty with many sewage plants is the sheer volume of liquid to be handled. This is aggravated where a xe2x80x9cmixedxe2x80x9d system, that is a system which carries both sewage and storm water is used. In many cases, sewage plants could handle more sewage if the quantity of liquid delivered therewith could be reduced, if, for example, liquid was removed from sewage before it enters trunk sewers. To date, this has not been considered feasible.
Also, there are regions where stormwater and sewage are received by the same system. This can cause difficulties where there are heavy rains which overload the system, as it is undesirable to permit raw sewage to pass to overflow.
3. Removal of pollutants from industrial wastes.
Many industrial plants must pay prohibitive rates to discharge polluted liquids into sewers. It would be most desirable to separate a part of the pollution before the waste is delivered to sewers and this would provide economies both to the plant and to the authority if this cost of the early removal of polluted matter was less than the cost, of cleaning up pollution later.
4. Separation of solids from liquid in industrial applications including food processing.
In our International Patent Application number PCT/AU94/00061, we disclosed and claimed apparatus and methods for separating solids from flowing liquids. We believe that the apparatus and methods disclosed in that application provide very good results in applications requiring the separation of solids from flowing liquids. We have now developed improvements and/or refinements to the invention disclosed in that application, which we believe provide even better results than those disclosed in our earlier application.
The principal object of the invention is to provide nonmechanical methods of and apparatus for separating floating and suspended solids from flowing liquids.
The invention, in a broad sense, comprises a means for the separation of solid matter from a liquid including a perforated separation panel through which the liquid is adapted to pass and which prevents the passage of the solid matter of a size larger than a predetermined size characterised in that when solid matter becomes located against the panel, the flow of liquid along the face of the panel on which the solid matter is located will tend to cause it to move from the panel so that the panel is self cleaned and does not become obstructed by the solid matter.
In a specific aspect, the invention provides a non-mechanical method for separating solids from a flowing liquid by utilising the energy of the flowing liquid on the inlet side, a separation panel in the path of the fluid flow and so arranged that the liquid is deflected thereby, which deflection causing larger suspended solids to a collection sump or the like. At the same time, the liquid flow across the separation panel prevents the panel from clogging. Liquid containing some finer suspended solids can pass through the panel to the outlet side. Floating solids are retained in the collection sump behind a flow direction baffle and can be prevented from inadvertent delivery during high flow conditions by a high level baffle located adjacent the top of the separation panel.
The invention also provides an apparatus for the separation of solids from a flowing liquid which apparatus has an inlet and an outlet for the liquid, a separation panel in the path of flow between the inlet and the outlet, the panel presenting a closed face in the direction of flow but apertures therethrough at an angle thereto, liquid being able to pass through the apertures whereas solids are caused to pass over the face thereof.
The arrangement is such that even solids smaller than the size of the apertures can be caused to move past the apertures either because of the inertia of the solids, or the action of gravity, or both.
In this specification, where we refer to water flow, this is intended to include relative water flow and thus there can be circumstances where the separation plate is moving as well as, or instead of, the water.
In a broader aspect, the present invention provides an apparatus for separating solid or particulate matter from a flowing liquid or gas, the apparatus including:
a separation panel positioned in the path of flow of the liquid or gas, the separation panel including a plurality of openings, wherein the openings are of a predetermined size such that only solid or particulate matter smaller than that size is able to pass through the openings, and wherein further, the configuration and arrangement of the openings on the separation panel is such that in use of the apparatus, solid or particulate matter larger than the predetermined size is substantially prevented from adhering to or obstructing the separation panel.
Preferably, the arrangement of the openings in the separation panel is such that, in use of the apparatus, the openings are disposed at an angle relative to the direction of flow of the liquid or gas.
Preferably further, the configuration of the openings is such that each opening includes a deflection means generally opposed to the direction of flow of the liquid or gas, to assist in deflecting solid or particulate matter entrained in the flow, away from the openings.
In a preferred form of the invention, the separation panel takes the form of a curved structure.
It is particularly preferred that the apparatus includes a generally cylindrical separation panel. It is particularly preferred that the separation panel is in the form of an open ended generally cylindrical structure. In this preferred form of the invention, it is also preferred that the separation panel forms part of a larger separation chamber, into which, in use of the apparatus, the liquid or gas flow is introduced by an inlet means, so as to establish a circular flow of the liquid or gas within the separation panel. This circular flow enables solids or particulate matter of a predetermined size entrained in the liquid or gas, to be trapped and to circulate within the confines of the separation panel. The circular motion of the flowing liquid or gas within the separation panel also results in the entrained solids or particulate matter generally not adhering to the separation panel, but being entrained in the circular motion of the liquid or gas. In this way, the establishment of a circular flow motion of the gas or liquid within the separation panel is such as to enable the separation panel to act as a generally self-cleaning filter for the solid or particulate matter entrained within the flowing liquid or gas. The fact that the liquid or gas is able to pass freely through the openings in the separation panel means that the panel is able to filter solid or particulate matter of a predetermined size from the flowing liquid or gas, thereby enabling the liquid or gas to be discharged to an outlet means, at least substantially filtered of the solid or particulate matter.
It is also preferred that the configuration of the apparatus is such that in use, the flow of the liquid or gas outside the confines of the separation panel is in a direction opposite to the direction of flow of the liquid or gas within the confines of the separation panel. Such a configuration assists in maintaining the self-cleaning function of the separation panel, in use of the apparatus.
Preferably, the apparatus also includes means for facilitating the collection of the solid or particulate matter into a receptacle, from which it may be removed. In some embodiments of the invention, gravitational forces may combine with the circular motion of the gas or liquid within the cylindrical separation panel, so as generally to encourage the deposition of the solid or particulate matter into a receptacle which may be positioned generally below and/or above the separation panel, depending upon the specific gravity of the solid or particulate matter. In the case of solids or particulate matter having a lower specific gravity than the liquid or gas, they will tend to float on the surface of the liquid or gas, in which case, they can be collected by a receptacle generally disposed above the separation panel. In the case of solids or particulate matter having a higher specific gravity than the liquid or gas, they will tend to settle under the action of gravitational forces, in which case, a receptacle to capture them will generally be positioned below the separation panel.
The apparatus may also include mechanical means to assist the deposition of the solid or particulate matter in the receptacle, through the action of gravity. Such means could take any number of forms, but would include, for example, providing the receptacle with a baffle or flange directed downwardly to encourage the deposition of settleable solid or particulate matter.
The invention also provides a method for separating solid or particulate matter from a flowing liquid or gas, the method including the steps of:
positioning a separation apparatus in the path of flow of the liquid or gas; and
providing the separation apparatus with a separation panel having a plurality of openings therethrough, wherein the openings are of a predetermined size such that only solid or particulate matter smaller than that size is able to pass through the openings, and wherein further, the configuration and arrangement of the openings on the separation panel is such that in use of the apparatus, solid or particulate matter larger than the predetermined size is substantially prevented from adhering to, or obstructing the separation panel.
Preferably further, in the method, the arrangement of the openings is such that, in use of the apparatus, the openings are disposed at an angle relative to the direction of flow of the liquid or gas.
It is also preferred, in the method, that each of the openings includes a deflection means generally opposed to the direction of flow of the liquid or gas, to assist in deflecting solid or particulate matter entrained in the flow, away from the opening.
Preferably, in the method described above, the separation panel takes the form of a curved structure.
Preferably further, in the method described above, the separation panel takes the form of a generally cylindrical structure, and the separation apparatus includes inlet and outlet means for directing the flow of the liquid or gas into, and out of, the separation apparatus respectively. It is particularly preferred that the separation panel is an open ended generally cylindrical structure.
It is particularly preferred in the said method, that the arrangement is such that the liquid or gas is introduced into the separation apparatus via the inlet means and presented to a separation chamber which includes a generally cylindrical separation panel, so that a circular motion of the liquid or gas is established within the confines of the separation panel, so as generally to trap solid or particulate matter of a pre-determined size within the separation panel, yet at the same time, permit the liquid or gas to pass therethrough freely, and so that the separation panel is continually cleaned by the circular motion of the liquid or gas within it.
Preferably further, in the method, the configuration of the apparatus is such that in use, the flow of the liquid or gas outside the confines of the separation panel is in a direction opposite to the direction of flow of the liquid or gas within the confines of the separation panel, so as to assist in maintaining the self-cleaning function of the separation panel, in use of the apparatus.
Preferably further, the method also includes the step of providing means to facilitate the collection of the solid or particulate matter separated by the method, from the flowing liquid or gas. Such means could, for example, utilise the assistance of gravitational forces, to assist in the collection of the solid or particulate matter.
Preferably further, the method also includes means for facilitating the removal from the separation apparatus, of solids or particulate matter separated from the flowing liquid or gas.